The proposed study is designed to elucidate some of the hazards that may confront both pregnant and non-pregnant females engaged in occupations in which pesticide exposure is a distinct possibility. This investigation will explore the effects of pesticide exposure on embryonic gonadal development and on basic reproductive processes on the sexually mature female. Pre-incubation exposure of chick eggs to dosages of DDT ranging from 2.5-25 mg. had little effect on the mortality of the embryos by five days of incubaton, whereas, when these same embryos were examined at 12 days of incubation animals exposed to dosages lower than 5 mg. had a mortality of less than 50%. Those exposed to higher dosages displayed a mortality of between 70 and 90%. Thus, more than five days are required forincorporation of high dosages of this agent into the chick embryo with resultant death. Whether alterations in gonadal development as a result of DDT are occurring prior to five days of development in animals exposed to either the high or low dosages ic currently being evaluated both histologically and histochemically. At all dosage levels tested there appeared to be no predominance of one sex over the other, which appears to eliminate any marked estrogenic effect of DDT at this early stage of development.